
B–62073E–1/042. INTERFACE BETWEEN CNC AND PMC–NA OR NB
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2.3.45 Servo off
(a) Servo off signals (SVF1, SVF2, SVF3, ...)
[Classification]
Input signals
[Function] Place the controlled axes in the servo off state; that is, they stop the current to the servo motor,
which disables position control. However, the position detection feature functions continu-
ously, so the current position is not lost.
These signals are provided for the controlled axes on a one–to–one basis. A number ap-
pended to a signal represents a controlled axis number.
SVF 1
1 ……
2 ……
3 ……
:
:
:
:
Servo off for the first axis
Servo off for the second axis
Servo off for the third axis
[Operation] While a servo off signal is low, the corresponding axis is in the servo off state. In the servo
off state, position control is disabled. If the machine is moved by external force, it is left de-
viated. The deviation is handled in one of the following two methods, which can be selected
by parameter setting:
(1) The deviation is treated as a servo error and recorded in the error counter.
When the servo off signal goes high again, the machine moves to compensate for the
error.
(2) Follow–up
The position of the control unit is moved so that the error counter is set to 0, assuming
that moving the tool the distance equivalent to the deviation has been specified.
In this method, the machine is still in a deviated position after the servo off signal goes
high again. The position of the control unit, however, moves in correspondence with the
machine position. Therefore, executing an absolute command can move the machine
to the correct position.
[Use] Method (1) above is generally used to allow mechanical clamp while the controlled axis is in
stopped state. The purpose of this method is to protect the servo motor against excessive
current when the clamping force is larger than the force of the servo motor.
While a servo off signal is low, the interlock signal for the corresponding axis should generally
be set low.
NOTE Method (2) is generally used for the mechanical handle feature. This feature drives the motor
to move the tool.